Bitmap vector2


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Bitmap vector2

  1. 1. Analog versus bitmap images <ul><li>The visual world is analog, which is to say that real-world images is a continuous spectrum of colours. An analog image embodies an infinite number of details. </li></ul><ul><li>Infinity is uncomfortably large to a computer. A computer-stored image is split into little bits of light. </li></ul><ul><li>A bitmap is a matrix of coloured dots. </li></ul><ul><li>This should help illustrate the nature of a bitmap. The left side of the picture appears to be an analog image. The right side illustrates how the image is really constructed. </li></ul>
  2. 2. Analog versus bitmap images
  3. 3. Bitmaps, Pixels & Colours <ul><li>The coloured dots that make up a bitmap are properly called pixels. </li></ul><ul><li>Web pages are measured in Pixels but not in inches, picas. </li></ul><ul><li>In addition to providing your eyes with infinitely small details, the analog world presents it with images having the potential for an infinite number of possible colours. </li></ul><ul><li>colour is represented on a computer by using varying amounts of red , green and blue light. These are the primary colours of what's called &quot;additive&quot; colour - by adding percentages of red, green and blue, any colour can be created. </li></ul><ul><li>In the simplest sort of bitmapped image, each pixel is represented by three numbers to store the amounts of red, green and blue light that define the colour of the pixel in question. </li></ul>
  4. 4. True colour Bitmap <ul><li>The smallest useful object for storing numbers on a computer is a byte. </li></ul><ul><li>In this sort of bitmap, each pixel requires one byte for each colour index for a total of three bytes per pixel. </li></ul><ul><li>As a byte represents eight bits, each pixel requires 24 bits to store all its colour information. </li></ul><ul><li>This defines the maximum number of discrete colours this sort of bitmap can represent as 2 24 , or 16,777,216. </li></ul><ul><li>Such graphics are referred to as “True Colour&quot; images, or just as &quot;24-bit&quot; graphics. </li></ul>
  5. 5. Size consideration in a true-coloured bitmap image <ul><li>The lowest resolution for a monitor displaying a Windows desktop is 640 by 480 pixels. </li></ul><ul><li>In a bitmap of this resolution, then, there would be three bytes per pixel, for a total of 640 x 480 x 3 bytes, or about 900 kilobytes. </li></ul><ul><li>Bitmapped graphics are huge entities, and they become huger still as they get better looking. </li></ul>
  6. 6. Bit-Depth = colour-Depth <ul><li>Number of colours = 2^(Bit-depth) </li></ul><ul><li>Bit-depth is the number of bits. </li></ul><ul><ul><li>It is also called “colour resolution”. </li></ul></ul>2^24 = 16.7 million 16,777,215 colours 24-bits 2^16 = 65536 65,536 colours 16-bits 2^8 = 256 256 colours 8-bits 2^4 = 16 16 colours 4-bit 2^3 = 8 8 colours 3-bit 2^2 = 4 4 colours 2-bit 2^1 = 2 2 colours 1-bit Calcuation colour resolution Bit depth
  7. 7. 8-bit and 24-bit photos <ul><li>Can you see the difference? </li></ul>
  8. 8. Vector Graphics <ul><li>In addition to bitmap graphics, there are vector graphics . </li></ul><ul><li>Vector graphics define pictures as collections of lines, ellipses, triangles, polygons and other basic graphic &quot;primitives.&quot; </li></ul><ul><li>Vector graphics are limited to storing mechanical art </li></ul><ul><ul><li>they cannot handle photo realistic subject. </li></ul></ul><ul><li>Vector graphic formats include </li></ul><ul><ul><li>Encapsulated PostScript files, which use the extension EPS, </li></ul></ul><ul><ul><li>Corel Draw files, which use the extension CDR, </li></ul></ul><ul><ul><li>AutoCAD drawings, which use the extension DXF. </li></ul></ul>
  9. 9. Bitmap vs. Vector Graphics <ul><li>Vector graphics </li></ul><ul><ul><li>Describe object relationships; can be scaled to any desired size without pixellation </li></ul></ul>
  10. 10. Bitmap vs. Vector graphics
  11. 11. Bitmap and Vector graphics file format <ul><li>Vector-based files are more suitable for illustrations that require precise measurements. </li></ul><ul><ul><li>File names for vector-based images usually consist of extensions such as *.EPS , *.AI , *CDR , or *.DWG . </li></ul></ul><ul><li>Bitmap-based files are more suitable for photo-realistic images that require complex colour variations. </li></ul><ul><ul><li>File names for bitmap-based images usually consist of extensions such as *.PSD , *.JPG , *GIF , *.TIF , or *.BMP . </li></ul></ul>